Catalytic decomposition of tertiary butyl hydroperoxide

ABSTRACT

In order to prepare a feedstock, isobutane is reacted with oxygen in an oxidation zone to provide an oxidation product comprising a solution of tertiary butyl hydroperoxide in unreacted isobutane. A catalyst may be present to catalyze the reaction of the oxygen with the isobutane if desired. 
     The feedstock is charged to a catalytic decomposition zone wherein the tertiary butyl hydroperoxide is decomposed in the presence of an imidazole-promoted metal phthalocyanine catalyst to provide a decomposition reaction product characterized by a compartively high conversion rate and a compartively high selectively of tertiary butyl hydroperoxide to tertiary butyl alcohol.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the catalytic decomposition of tertiary butyl hydroperoxide. More particularly, this invention relates to a method for the preparation of tertiary butyl alcohol by the catalytic decomposition of tertiary butyl hydroperoxide. Still more particularly, this invention relates to a method wherein a metal phthalocyanine promoted with imidazole is used to catalyze the substantially selective decomposition of tertiary butyl hydroperoxide to tertiary butyl alcohol.

2. Prior Art

It is known to react isobutane with oxygen, either thermally or catalytically, to form a peroxidation reaction product wherein the principal peroxide that is formed is tertiary butyl hydroperoxide. It is also known to thermally or catalytically decompose the tertiary butyl hydroperoxide to form tertiary butyl alcohol.

The metal phthalocyanines are known compounds, described for example in the ACS Monograph Series by F. H. Moser and A. L. Thomas entitled "Phthalocyanine Compounds" (Rhinehold Publishing Corp.).

Williams et al. U.S. Pat. No. 3,816,548 is directed to a liquid phase oxidation process for oxidizing an isoparaffin hydrocarbon such as isobutane to an alcohol such as tertiary butyl alcohol in the presence of certain metal phthalocyanine catalysts.

Klein in U.S. Pat. No. 3,472,876, discloses the use of cobalt diimine chelates to catalyze the reaction of oxygen with an olefin to form an olefin epoxide.

Quin U.S. Pat. No. 2,854,487 discloses a process wherein isopropyl benzene, hydroperoxides are catalytically decomposed to form carbinols in the presence of hydrogen and a catalyst composed of palladium supported on activated alumina.

Grane U.S. Pat. No. 3,474,151 discloses that tertiary butyl alcohol starts to dehydrate at 450° C. and to decompose at a "rapid rate" at temperatures above 475° F. Grane discovered, however, that residual quantities of hydroperoxide contaminants present in tertiary butyl alcohol could be thermally decomposed by heating the contaminated tertiary butyl alcohol at a temperature of 375° to 475° F. for about 1 to 10 minutes. Heating tertiary butyl alcohol containing small amounts of peroxides at high temperatures for even short periods of time to remove the peroxides produces undesirable products such as isobutylene.

Grane et al. U.S. Pat. No. 4,294,999 discloses a process wherein isobutane is oxidized in a pressured reactor in the presence of a solubilized molybdenum catalyst to provide a mixture of tertiary butyl alcohol, tertiary butyl hydroperoxide, methanol, acetone, and other oxygen-containing compounds. The tertiary butyl hydroperoxide is thermally decomposed under pressure at about 280° F. to provide a tertiary butyl alcohol product containing only residual quantities of tertiary butyl hydroperoxide which are then decomposed in accordance with Grane U.S. Pat. No. 3,474,151 by heating the tertiary butyl alcohol at 375° to 475° for about 1 to 10 minutes.

Grane et al. U. S. Pat. No. 4,296,262 discloses a related process wherein isobutane is reacted with oxygen in a reaction zone for a residence tie of about 1 to 10 hours at a temperature of about 240° to about 340° F. and a pressure of about 100 to about 1000 psig. in the presence of a catalytically effective amount of a soluble molybdenum catalyst. A liquid stream comprising tertiary butyl alcohol is recovered from the reaction mixture and fed to a decomposition zone wherein the tertiary butyl hydroperoxide contained therein is decomposed by "hot aging" at 250-350° F. at a pressure lower than the pressure in the oxidation zone. The tertiary butyl alcohol can be further subjected to a clean-up treatment at 375-475° F. for 1to 10 minutes. Worrell et al. in U.S. Pat. No. 4,296,263 disclose a related process wherein the feedstock is a mixture of normal butane with isobutane and wherein the oxidation catalyst is a soluble form of chromium, cobalt, nickel, manganese, molybdenum, or a mixture thereof.

When isobutane is reacted with molecular oxygen, the principal products of the reaction are tertiary butyl alcohol and tertiary butyl hydroperoxide. However, minor amounts of other peroxides, including ditertiary butyl peroxide are also formed. Generally speaking, from about 10 to about 100 parts of tertiary butyl hydroperoxide are formed per part of ditertiary butyl peroxide. Minor quantities of other contaminants are also formed.

In addition, a minor amount of water will be formed, which will normally amount to about 0.5 to 1 wt.% of the reactor effluent. The amount of byproduct water that is produced is a function of the severity of the reaction conditions employed and will tend to increase as the severity of the reaction conditions is increased.

A listing of the components present in a representative reaction product, and their nominal boiling points is given in Table A.

                  TABLE A                                                          ______________________________________                                         Component          NBP (°C.)                                            ______________________________________                                         Isobutane          -11.7                                                       Methyl formate     31.8                                                        Acetone            56.3                                                        Isobutylene oxide  60.0                                                        Isobutylraldehyde  64.1                                                        Methanol           64.7                                                        Methyl-t-butyl peroxide                                                                           74.2                                                        Isopropyl alcohol  82.3                                                        Tertiary butyl alcohol                                                                            82.4                                                        Ditertiary butyl peroxide                                                                         111.0                                                       t-butyl-i-pr-peroxide                                                                             124.0                                                       Tertiary butyl formate                                                                            163.8                                                       ______________________________________                                    

The minor by-products are sometimes difficult to remove. For example, tertiary butyl formate has a higher boiling point than ditertiary butyl hydroperoxide but tends to distill overhead, which suggests that it forms a minimum boiling azeotrope with another component or components.

As indicated, tertiary butyl hydroperoxide is useful as a raw material for the manufacture of tertiary butyl alcohol. The tertiary butyl alcohol can be formed by catalytic decomposition of the tertiary butyl hydroperoxide. In the Williams et al. process disclosed in U.S. Pat. No. 3,472,876, an oxygen-containing gas was charged to a reactor containing isobutane and an oxidation catalyst to provide a reaction mixture comprising tertiary butyl alcohol, tertiary butyl hydroperoxide, acetone, and tertiary butyl ether. The reported results in the patent indicate that there was a comparatively low rate of conversion and a comparatively poor selectivity of the reaction to tertiary butyl alcohol.

SUMMARY OF THE INVENTION

In accordance with the present invention, isobutane is reacted with oxygen in an oxidation zone to provide an oxidation product comprising a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol and unreacted isobutane. A catalyst may be present to catalyze the reaction of the oxygen with the isobutane if desired.

A suitable feedstock is used, such as one prepared by the oxidation of isobutane with molecular oxygen to provide an oxidation reaction product containing a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol and unreacted isobutane. The feedstock may comprise tertiary butyl hydroperoxide dissolved in tertiary butyl alcohol which is recovered from the oxidation reaction product. The feedstock is charged to a catalytic decomposition zone wherein the tertiary butyl hydroperoxide is decomposed in the presence of an imidazole-promoted metal phthalocyanine catalyst to provide a decomposition reaction product characterized by a comparatively high conversion rate and a comparatively high selectivity of tertiary butyl hydroperoxide to tertiary butyl alcohol.

The tertiary butyl alcohol will not be the only decomposition product that is formed. A minor amount of ditertiary butyl peroxide will also be formed together with other oxygen-containing materials such as those listed above.

The tertiary butyl alcohol that is recovered from the decomposition reaction mixture will be contaminated with ditertiary butyl peroxide and other oxygenated impurities.

The ditertiary butyl peroxide can be recovered, if desired, by a process such as the process disclosed in copending Sanderson et al. U.S. patent application S.N. 06/945,628, filed Dec. 23, 1986, and entitled "Recovery of Purified Ditertiary Butyl Peroxide" or the process disclosed in copending application S.N. 06/945,629, filed Dec. 23, 1986 by Sanderson et al., and entitled "Ditertiary Butyl Peroxide Recovery".

If desired, the ditertiary butyl peroxide and other contaminants may be removed from the tertiary butyl alcohol product by a catalytic purification process such as, for example, the purification process disclosed in copending Sanderson et al. U.S. patent application S.N. 06/836,798, filed Mar. 6, 1986, now abandoned, and entitled "Removal of Peroxide Contaminants from Tertiary Butyl Alcohol Using a Nickel Catalyst", or by a purification process disclosed in copending Sanderson et al. U.S. patent application S.N. 06/926,159, filed Nov. 3, 1986, and entitled "Catalytic Removal of Peroxide Contaminants from Tertiary Butyl Alcohol.", now U.S. Pat. No. 4,742,179, issued May 3, 1988, or by the process disclosed in copending Sanderson et al., application S.N. 06/932,822, filed Nov. 20, 1986, and entitled "Catalytic Decomposition of Impurities in Tertiary Butyl Alcohol", now U.S. Pat. No. 4,705,903, issued Nov. 10, 1987, or, as yet another example, by the process disclosed in copending Sanderson et al. U. S. patent application S.N. 07/004,508, filed Jan. 30, 1987, now Pat. No. 4,873,380, and entitled "Catalyst for Removing Peroxide Contaminants from Tertiary Butyl Alcohol".

DESCRIPTION OF THE PROCESS OF THE PRESENT INVENTION

The starting materials for the process of the present invention are tertiary butyl hydroperoxide, a metal phthalocyanine catalyst, such as a metal phthalocyanine of the type disclosed in Williams et al. U. S. Patent No. 3,816,548, imidazole, and a solvent.

The metal phthalocyanine catalyst used in this invention is suitably a phthalocyanine of a heavy metal selected from the Group IB, Group VIIB, or Group VIIIB of the Periodic Table.

Phthalocyanine itself is: ##STR1##

The two hydrogens in the center of the molecule are replaced by metals from these groups. The metals may be in a high oxidation state or a lower oxidation state. For example, Ferric (Fe⁺⁺⁺) or Ferruus (Fe⁺⁺) may be used. In addition, from 1 to 16 of the peripheral hydrogen atoms on the 4 benzene rings may be replaced with halogen atoms and by numerous organic and inorganic groups. Suitable phthalocyanines include cobalt phthalocyanine, copper phthalocyanine, chloroferric phthalocyanine, ferrous phthalocyanine, manganese phthalocyanine, and ruthenium phthalocyanine.

The solvent to be used in practicing the process of the present invention may be any suitable organic solvent in which tertiary butyl hydroperoxide is soluble at least to an extent sufficient to provide a solution containing from about 5 to about 30 wt.% of tertiary butyl hydroperoxide. A preferred solvent is isobutane and a still more preferred solvent is tertiary butyl alcohol or a mixture thereof with isobutane. In accordance with the most preferred embodiment of the present invention, the charge material for the process will comprise about a 5 to about a 30 wt.% solution of tertiary butyl hydroperoxide and tertiary butyl alcohol.

The process of the present invention may be conducted batchwise in kettles or by continuously passing the reactants through a reactor.

In any event, the solvent solution of tertiary butyl hydroperoxide that is charged to the reaction zone will also have dissolved or slurried therein from about 0.001 to about 5 wt.%, based on the weight of the tertiary butyl hydroperoxide, of a metal phthalocyanine catalyst and from about 0.2 to about 5 parts by weight, per part of metal phthalocyanine catalyst, of imidazole. The imidazole is preferably used in an amount correlated with the reaction conditions and the metal phthalocyanine catalyst sufficient to provide at least about a 90% conversion of the t-butyl hydroperoxide and a selectivity of the t-butyl hydroperoxide to t-butyl alcohol of at least about 90% on the basis of t-butyl hydroperoxide charged.

The catalytic decomposition f the tertiary butyl hydroperoxide is preferably conducted at a temperature within the range of about 20° to about 120° C. and, more preferably, at a temperature within the range of about 30 t about 60° C. The reaction is preferably conducted at autogeneous pressure although about 0 to 1,000 psig or superatmospheric pressures up to about 1000 psig. may be used, if desired.

Flow rates of the charge solution to the reaction zone should be adjusted in order to provide an appropriate contact time within the reactor. In a batch process, the holding time may suitably be from about 0.5 to about 10 hours.

In accordance with the most preferred embodiment of the present invention, isobutane is reacted with oxygen in an oxidation zone under oxidation reaction conditions including a temperature of about 135° to about 155° C., a pressure of about 300 to about 800 psig., and a holding time of about 2 to about 6 hours to provide an initial oxidation reaction product comprising unreacted isobutane, tertiary butyl hydroperoxide, and some tertiary butyl alcohol. The oxidation reaction product is fractionated in any appropriate manner (e.g., y distillation in a distillation zone) to remove the isobutane therefrom for recycle and to provide a solution of tertiary butyl hydroperoxide and tertiary butyl alcohol which will normally contain from about 5 to about 30 wt.% of tertiary butyl hydroperoxide. If the tertiary butyl hydroperoxide concentration i excessive, additional tertiary butyl alcohol may be added.

The solvent solution of tertiary butyl hydroperoxide in organic solvents (e.g., tertiary butyl alcohol solvent solution of tertiary butyl hydroperoxide) is ten charged to a catalytic hydroperoxide decomposition zone where it is brought into contact with an imidazole-promoted metal phthalocyanine catalyst to substantially selectively convert the tertiary butyl hydroperoxide to tertiary butyl alcohol with high yields and selectivities.

As indicated, the catalytic decomposition of the tertiary butyl hydroperoxide in the catalytic hydroperoxide decomposition reaction zone may suitably be conducted at a temperature within the range of about 20° to 120° C. (and more preferably from about 30° to about 60° C.) at autogeneous pressure or if desired at a superatmospheric pressure up to 1000 psig. for a contact time within the range of about 0.5 to about 10 hours.

The reaction product from the tertiary butyl hydroperoxide decomposition step may then be fractionated in any suitable manner, such as, for example, in the manner shown in the process disclosed in above identified copending U.S. patent application S.N. 06/945,628 filed Dec. 23, 1986. In accordance with a process recovery sequence of this nature, both the tertiary butyl alcohol and the ditertiary butyl peroxide will be recovered in purified form as products of the reaction.

Alternately, a crude tertiary butyl alcohol product stream contaminated with ditertiary butyl peroxide and other contaminants may be obtained which will then be further treated either thermally, in accordance with the process of the Grane et al. U. S. patents, or catalytically by one of the processes disclosed in the copending Sanderson et al. patent applications to convert the ditertiary butyl peroxide to tertiary butyl alcohol and to otherwise significantly reduce the level of contamination of the other oxygencontaining impurities.

SPECIFIC EXAMPLES

The invention will be further illustrated by the following specific examples which are given by way of illustration and not as limitations on the scope of this invention.

Procedure: Tube Experiments

A 150-ml Fisher-Porter pressure tube equipped with pressure gauge, rupture disk, and shut-off valve was charged with 15.0g of a 20% TBHP solution in TBA, and catalyst(s). the tube was suspended in a constant temperature bath (+or -0.2° C.) for the desired period of time at the required temperature. The tube was shaken from time to time during the run. At the end of the run, the tube was placed in cold water (15-20° C.) for 15 minutes. The pressure was then slowly released. The contents were analyzed by GC. The results are shown in the attached Table I.

Procedure: Autoclave Experiment

A 1000 cc stainless-steel autoclave equipped with Magne-drive stirrer, cooling coils, electric heater, etc., was charged with 300.0g 20% TBHP in TBA along with catalyst. The mixture was then sealed, stirred at 300 rpm, and heated to the desired temperature for the required time. The mixture was then cooled to ambient temperature, slowly vented, and the contents transferred to a tared container. The liquid contents were analyzed by GC.

                                      TABLE I                                      __________________________________________________________________________     Decomposition of 20% TBHP (in TBA) in the Presence                             of Various Phthalocyanines Plus Imidazole                                                                  Wt. %                                              N.B.        Time                                                                              Temp                                                                               Reac-        Ace-                                           No.                                                                               Catalyst(s).sup.a                                                                       (Hr)                                                                              (°C.)                                                                       tor.sup.b                                                                          TBHP %                                                                              TBA tone                                                                              MeOH                                                                               DTBP                                    __________________________________________________________________________     6261                                                                           15 Mn(II)PCY[.30 g]                                                                        4.0                                                                               40.0                                                                               C   5.528                                                                               91.808                                                                             0.312                                                                             <0.1                                                                               2.052                                   24 Mn(II)PCY[ g]                                                                           4.0                                                                               40.0                                                                               C   0.891                                                                               95.413                                                                             0.658                                                                             <0.1                                                                               2.585                                      IM [1.0 g]                                                                  28 Fe(III)PCYCl                                                                            0.5                                                                               40.0                                                                               T   1.882                                                                               94.886                                                                             0.558                                                                             <0.1                                                                               2.249                                      [.01 g]                                                                     30 Fe(III)PCYCl                                                                            0.5                                                                               40.0                                                                               T   3.439                                                                               93.587                                                                             0.435                                                                             <0.1                                                                               2.098                                      [.01 g] IM [.01 g]                                                          31 Mn(II)PCY[.30 g]                                                                        4.0                                                                               40.0                                                                               C   2.774                                                                               93.936                                                                             0.450                                                                             <0.1                                                                               2.415                                      IM [.50 g]                                                                  32 Fe(III)PCYCl                                                                            1.0                                                                               40.0                                                                               T   0.656                                                                               95.767                                                                             0.677                                                                             <0.1                                                                               2.243                                      [.01 g] IM [.01 g]                                                          25 Fe(III)PCYCl                                                                            1.0                                                                               40.0                                                                               T   1.882                                                                               94.962                                                                             0.519                                                                             <0.1                                                                               2.290                                      [.01 g]                                                                     33 VOPCY [.01 g]                                                                           7.0                                                                               40.0                                                                               T   N.R..sup.c                                                                          --  -- --  --                                      34 VOPCY [.01 g]                                                                           5.0                                                                               40.0                                                                               T   N.R..sup.c                                                                          --  -- --  --                                         IM [0.1 g]                                                                  36 Mn(II) PCY                                                                              4.0                                                                               40.0                                                                               C   1.282                                                                               95.189                                                                             0.540                                                                             <0.1                                                                               2.515                                      [.30 g] IM [.70 g]                                                             Starting Material                                                                       -- --  --  20.345                                                                              79.345                                                                             0  0   0.045                                   __________________________________________________________________________      .sup.a PCY = phthalocyanine                                                    IM = imidazole?                                                                .sup.b T = 150 cc FisherPorter pressure tube, 15.0 g scale                     C = 1000 cc stainless steel autoclave, 300 g scale                             .sup.c N.R. = no detectable reaction                                     

With reference to the table, it ill be noticed that the use of imidazole as a promoter resulted in an enhanced rate of decomposition of the tertiary butyl hydroperoxide as shown by the increased conversion for the given reaction time and an enhanced selectivity of the tertiary butyl hydroperoxide to tertiary butyl alcohol. 

Having thus described our invention, what is claimed is:
 1. In a method wherein a t-butyl hydroperoxide charge stock is continuously brought into contact with a catalytically effective amount of a reduction catalyst in a reaction zone in liquid phase with agitation to convert said t-butyl hydroperoxide to decomposition products, principally t-butyl alcohol, the improvement which comprises:(a) using, as said reduction catalyst, a metal phthalocyanine catalyst, the metal of said metal phthalocyanine catalyst being a heavy metal selected from the group consisting of heavy metals of Group IB, Group VIIB and Group VIIIB of the Periodic Table. (b) promoting the catalytic activity of said metal phthalocyanine catalyst with imidazole, and (c) recovering said t-butyl alcohol from the products of said reaction.
 2. In a method wherein a t-butyl hydroperoxide charge stock is continuously brought into contact with a catalytically effective amount of a reduction catalyst in a reaction zone in liquid phase under reaction conditions including a temperature within the range of about 20° to about 120° C. and a pressure of about 0 to about 1000 psig to convert said t-butyl hydroperoxide to decomposition products, principally t-butyl alcohol, the improvement which comprises:(a) using, as said reduction catalyst, about 0.001 to about 5 wt.%, based on the weight of the charge stock, of a metal phthalocyanine catalyst, the metal of said metal phthalocyanine catalyst being a heavy metal selected from the group consisting of heavy metals of Group IB, Group VIIB and Group VIIIB of the Periodic Table, (b) promoting the catalytic activity of said metal phthalocyanine catalyst with imidazole, said imidazole being used in an amount within the range of 0.2 to about 5.0 parts by weight per part of metal phthalocyanine catalyst, correlated with said reaction conditions and the amount of said metal phthalocyanine catalyst sufficient to provide at least about 90% conversion of said t-butyl hydroperoxide and selectivity of said t-butyl hydroperoxide to t-butyl alcohol of at least about 90% on the basis of t-butyl hydroperoxide charged, and (c) recovering said t-butyl alcohol from the products of said reaction.
 3. In a method wherein a t-butyl hydroperoxide charge stock is continuously brought into contact with a catalytically effective amount of a reduction catalyst in a reaction zone in liquid phase under reaction conditions including a temperature within the range of about 30° C. to about 60° C. and a pressure of about 0 to about 1000 psig. to convert said t-butyl hydroperoxide to decomposition products, principally t-butyl alcohol, the improvement which comprises:(a) using, as said reduction catalyst, about 0.001 to about 5 wt.%, based on the weight of the charge stock, of a metal phthalocyanine catalyst, the metal of said metal phthalocyanine catalyst being a heavy metal selected from the group consisting of heavy metals of Group IB, Group VIIB and Group VIIIB of the Periodic Table, (b) promoting the catalytic activity of said metal phthalocyanine catalyst with from about 0.2 to about 5 parts by weight, per part of said metal phthalocyanine catalyst of imidazole, and (c) recovering said t-butyl alcohol from the products of said reaction.
 4. A method as in claim 3 wherein the metal phthalocyanine is manganous phthalocyanine.
 5. A method as in claim 3 wherein the metal phthalocyanine is chloroferric phthalocyanine.
 6. In a continuous method for preparing t-butyl alcohol wherein isobutane is continuously reacted with molecular oxygen in an initial oxidation zone to provide an initial oxidation reaction product comprising unreacted isobutane and isobutane oxidation reaction product, principally t-butyl hydroperoxide and said t-butyl hydroperoxide is continuously brought into contact with a catalytically effective amount of a phthalocyanine catalyst in a reaction zone under liquid phase reaction conditions including a temperature within the range of about 20° to about 120° C. and a pressure of about 0 to about 1000 psig. to convert said t-butyl hydroperoxide to decomposition products, principally t-butyl alcohol, the improvement which comprises:(a) using, as said phthalocyanine catalyst, about 0.001 to about 5 wt. %, based on the weight of said t-butyl hydroperoxide, of a heavy metal phthalocyanine catalyst, the heavy metal of said heavy metal phthalocyanine catalyst being a heavy metal selected from the group consisting of heavy metals of Group IB, Group VIIB and Group VIIB of the Periodic Table, (b) promoting the catalytic activity of said metal phthalocyanine catalyst with from about 0.2 to about 5 parts by weight, per part of said metal phthalocyanine catalyst of imidazole, and (c) recovering said t-butyl alcohol from the products of said reaction.
 7. In a continuous method of preparing t-butyl alcohol wherein isobutane is continuously noncatalytically reacted with molecular oxygen in an initial oxidation zone to provide an initial oxidation reaction product comprising unreacted isobutane t-butyl hydroperoxide, some tertiary butyl alcohol, and a minor amount of ditertiary butyl peroxide, wherein said initial oxidation reaction product is fractionated to remove unreacted isobutane and to provide a feedstock comprising a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol and wherein said feedstock is continuously brought into contact with a catalytically effective amount of a phthalocyanine catalyst in a reaction zone under liquid phase reaction conditions including a temperature within the range of 20° to about 120° C. and a pressure of about 0 to about 1000 psig. to convert said t-butyl hydroperoxide to decomposition products, principally t-butyl alcohol, and including ditertiary butyl peroxide and to provide a conversion reaction mixture, the improvement which comprises:(a) using, as said phthalocyanine catalyst, about 0.001 to about 5 wt. %, based on the weight of the feed stock, of a heavy metal phthalocyanine catalyst, the metal of said metal phthalocyanine catalyst being a heavy heavy metal selected from the group consisting of heavy metals of Group IB, Group VIIB and Group VIIIB of the Periodic Table, (b) promoting the catalytic activity of said metal phthalocyanine catalyst with from about 0.2 to about 5 parts by weight, per part of said metal phthalocyanine catalyst of imidazole, and (c) continuously removing a stream of said conversion reaction mixture from said reaction zone, (d) continuously fractionating said stream of said conversion reaction mixture to obtain a crude t-butyl alcohol fraction contaminated with ditertiary butyl peroxide, (e) treating said crude t-butyl alcohol fraction to convert said ditertiary butyl peroxide to tertiary butyl alcohol, and (f) continuously recycling said isobutane fraction recovered from said initial oxidation reaction product to said initial oxidation zone.
 8. A method as in claim 7 wherein the metal phthalocyanine is manganous phthalocyanine.
 9. A method as in claim 7 wherein the metal phthalocyanine is chloroferric phthalocyanine. 